Reincarnated as the Weakest Noble Son, I Master Dark Magic

Oukoku o Ura kara Shihai Suru Akuyaku Kizoku no Suekko ni Tensei Shimashita ~“Aitsu wa Kyoudai no Naka de Saijaku” no Chuu Boss da kedo Geemu Chishiki de Yami Mahou o Kiwamete Saikyou o Mezasu~ / 王国を裏から支配する悪役貴族の末っ子に転生しました ～「あいつは兄弟の中で最弱」の中ボスだけどゲーム知識で闇魔法を極めて最強を

The Balfont family secretly controls the kingdom from the shadows, handling warfare, assassination, and espionage. I was reincarnated as their youngest son, Alphis, a so-called “mid-boss” despised by his older brothers as the weakest among them. However, armed with my extensive knowledge of a game I’ve played countless times, I have the potential to become stronger than anyone else!? I’ll master dark magic and aim to become the strongest in the world! A thrilling rise-to-power story begins, as I crush everything in my path—even the game’s original storyline!